[Flow] Exception on indexed access types

[pascalduez]

Using recent Flow "indexed access types" we get the following exception:

did not recognize object of type "IndexedAccessType"

See https://flow.org/en/docs/types/indexed-access

react-docgen@5.4.0

benjamn/ast-types#596

[pascalduez]

Support for IndexedAccessType added from ast-types@0.15.0.